Mercruiser 140 split intake/exhaust manifold

[griff]

I have searched several forums and can find no answer. I have a 72' mercruiser 140 3.0 L4 I/O S/N 2770087. As you may already know the intake and exhaust run throught the same manifold. I was wondering if anyone had ever welded up their own sheetmetal intake and exhaust to split the two and reduce intake air charge temps? The placard on the top of the engine states to use only 93 or higher premium leaded fuel. I figure this is to reduce detonation from high intake air temps. Instead of running high octane fuel and lead substitute to reduce engine knock I want to simply reduce air temps. Is their is a two sided cylinder head like modern cars that would swap onto the merc 140 block? Just an idea right now. Maybe it could get me a few more hp from the stock motor. And has anyone ever monitored intake temps at the ports on this motor.

 

[griff]

Re: Mercruiser 140 split intake/exhaust manifold

Bump

 

[JustJason]

Re: Mercruiser 140 split intake/exhaust manifold

Well.... a 140 didn't come out untill 82... So who knows what ya really got. your serial makes it an early 70's 120.
Not that it matters...... because..... there's nothing you can do with that manifold. It is what it is.
Now... If your having detonation issues... you need to start pulling your timing back a few degrees at a time until it goes away.

 

[griff]

Re: Mercruiser 140 split intake/exhaust manifold

It says 140hp on top of the valve cover. Casting # on the block is 2770087. Cant remember the head casting #. I was justwondering if some homemade headers would work on this engine.

 

[JustJason]

Re: Mercruiser 140 split intake/exhaust manifold

who know's what coulda been swapped on that motor in the last 36 years.....
Go by whats on the ID Tag
and nothings gonna work.... nothing that's coast guard legal anyways...
read my sig

 

[griff]

Re: Mercruiser 140 split intake/exhaust manifold

I guess I wont really know untill I start pullnig everything apart and rebuilding it. By the way this is a restoration project. I know alot about car engines but not that much yet about marine engines. Getting as much knowledge as I can from this awsome site and it repertoire of gurus.